GP Suspension
Well-known member
There has been some debate recently over re-valving versus replacement of the sogi cartridges but little mention of the different alloys utilized. The sogi units utilize a 20mm cartridge body made from 7075-T6 aluminum. This has nearly 3 times the tensile strength and is also a much harder alloy than the 6061-T6 aluminum used in ak-20 cartridges. The ak-20 cartridges are however hard coated for wear.
The sogi metering rod is made from mild steel and is 10mm in diameter, where as the ak-20 uses a 12.5mm metering rod made from 6061-T6 and hard coated for wear. It has been our experience over the past 12 years that you can achieve good damping forces with either size metering rod.
As to the cartridge body wearing out prematurely we have yet to see an example of this with the factory 7075-T6 alloy. Teflon bushings immersed in fork oil will not result in any measurable amount of wear as long as service intervals are maintained. However on rare occasion the top seal head bushing has shown wear and can be replaced when revalving.
If you are concerned about cartridge tube wear I recommend that you inspect your inner lower aluminum stanchions tube near the brakes. Any wear due to poor maintenance will be evident there first due to the loads of the motorcycle fork angle during braking. We have seen wear in this area due to lack of maintenance (riding on blown seals) but even then wear in the cartridge tube is rare.
It has been suggested that you can not get state of the art damping with a revalve approach however this is not accurate. Damping performance has much more to do with the compression and rebound kit engineering. Tube and rod construction are secondary and if the tube is not worn, replacing the tube will not result in any measurable improvement in performance.
Why don't we sell a new 20mm cartridge? We have the production capability to do so, and in fact we offer a complete 25mm upgrade cartridge with a 7075-T6 hard coated tube with a seamless stainless metering rod for more race-oriented customers. However in our opinion the 20mm OEM cartridge provides excellent performance after revalve and respring at half the cost of replacement.
Will you notice a difference between stock performance and a revalve job with new springs? We have revalved several thousand forks over the last 12 years and overwhelmingly customer feedback has been that they noticed a considerable improvement over stock performance. Here's what one recent customer had to say.
"I left you with a very good bike that had what anyone would think of as a more than adequate suspension with more than adequate capabilities. What I got back was something else. What I picked up and took for its
first ride was an entirely new machine. Clearly, the chassis was capable of a lot more than the original
front forks and rear shock would allow. Immediately, several things were evident: Increased lean angles that I had not been able to achieve without touching down or wallowing were easily achieved. Elevated corner speeds were possible because the rear end was no longer upset by irregular pavement. Higher average speeds and higher gear choices in twisties came easily as the chassis is no longer upset by anything.
I have confidence in being able to enter corners at any lean angle the tires can take without scraping a
peg. I feel 100% safer on my bike as I now am confidant in its abilities. While this bike retains all of its touring capabilities, it now has the sporting capabilities I so dearly missed! I am now able to use the whole tire-right to the edge-as it was designed to be used. It is now possible to have the Sport part of the
sport/touring experience. The bike is 100% more comfortable as the suspension works so much better at smoothing out road irregularities, even during non-aggressive riding. I am able to exercise the really good engine of this bike at will as the suspension is capable of handling more aggressive corner exit speed and more aggressive side to side transitions. The fully adjustable suspension allows for easy adjustment for passenger or luggage weight variations. The point to all this is that the result of your work exceeded my expectations. I now really love to ride this bike, where I used to just like to ride it." Victor Pritzker 2005 FJR1300.
The sogi metering rod is made from mild steel and is 10mm in diameter, where as the ak-20 uses a 12.5mm metering rod made from 6061-T6 and hard coated for wear. It has been our experience over the past 12 years that you can achieve good damping forces with either size metering rod.
As to the cartridge body wearing out prematurely we have yet to see an example of this with the factory 7075-T6 alloy. Teflon bushings immersed in fork oil will not result in any measurable amount of wear as long as service intervals are maintained. However on rare occasion the top seal head bushing has shown wear and can be replaced when revalving.
If you are concerned about cartridge tube wear I recommend that you inspect your inner lower aluminum stanchions tube near the brakes. Any wear due to poor maintenance will be evident there first due to the loads of the motorcycle fork angle during braking. We have seen wear in this area due to lack of maintenance (riding on blown seals) but even then wear in the cartridge tube is rare.
It has been suggested that you can not get state of the art damping with a revalve approach however this is not accurate. Damping performance has much more to do with the compression and rebound kit engineering. Tube and rod construction are secondary and if the tube is not worn, replacing the tube will not result in any measurable improvement in performance.
Why don't we sell a new 20mm cartridge? We have the production capability to do so, and in fact we offer a complete 25mm upgrade cartridge with a 7075-T6 hard coated tube with a seamless stainless metering rod for more race-oriented customers. However in our opinion the 20mm OEM cartridge provides excellent performance after revalve and respring at half the cost of replacement.
Will you notice a difference between stock performance and a revalve job with new springs? We have revalved several thousand forks over the last 12 years and overwhelmingly customer feedback has been that they noticed a considerable improvement over stock performance. Here's what one recent customer had to say.
"I left you with a very good bike that had what anyone would think of as a more than adequate suspension with more than adequate capabilities. What I got back was something else. What I picked up and took for its
first ride was an entirely new machine. Clearly, the chassis was capable of a lot more than the original
front forks and rear shock would allow. Immediately, several things were evident: Increased lean angles that I had not been able to achieve without touching down or wallowing were easily achieved. Elevated corner speeds were possible because the rear end was no longer upset by irregular pavement. Higher average speeds and higher gear choices in twisties came easily as the chassis is no longer upset by anything.
I have confidence in being able to enter corners at any lean angle the tires can take without scraping a
peg. I feel 100% safer on my bike as I now am confidant in its abilities. While this bike retains all of its touring capabilities, it now has the sporting capabilities I so dearly missed! I am now able to use the whole tire-right to the edge-as it was designed to be used. It is now possible to have the Sport part of the
sport/touring experience. The bike is 100% more comfortable as the suspension works so much better at smoothing out road irregularities, even during non-aggressive riding. I am able to exercise the really good engine of this bike at will as the suspension is capable of handling more aggressive corner exit speed and more aggressive side to side transitions. The fully adjustable suspension allows for easy adjustment for passenger or luggage weight variations. The point to all this is that the result of your work exceeded my expectations. I now really love to ride this bike, where I used to just like to ride it." Victor Pritzker 2005 FJR1300.
